Rubbing machine



H. B. SCOTT RUBBING MACHINE Original Filed May 31. 1922 Jan.,15, 1929.

4 Sheets*$heet l FIG.1

Howard B Scott M W Jan. 15, 1929. 1,699,029

H. B. SCOTT RUBBING MACHINE Original Filed May 31. 1922 4 sheets sheet 2 4 v uwiuw I By We? Hiudm Jan. 15,1929.

. 1,699,029 H. B. sco'r'r RUBBING MACHINE Original Filed May 51, 1922 4 Sheets-Sheet 5 W, FIG.8

gwuamtoc Howard B. Scott BY M 196W Jan. 15, 1929. 1,699,029

H, B SCOTT -RLIBBING MACHINE Original Filed May 31, 1922' 4 s t -s t, 4

FIG.1O

Howard B. Scott Patented Jan. 15, 1929.

' UNITED STATES 1 PATENT OFFICE.

. HOWARD B. SCOTT, OF DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE NATIONAL CASH REGISTER COMPANY, OF DAYTON, OHIO, A CORPORATION OF MARYLAND.

RUBBING MACHINE.

Original application filed May 31, 1922, Serial No. 564,774, and in Germany October 25, 1922. Divided. and

i this application filed March 26, 1923, Serial No. 627,777.

The subject matter of this application constitutes a division of an application of Howard B. Scott, Serial No. 564,771, filed May 31, 1922.

This invention relates to portable rubbing machines and the like, particularly adapted for use in finishing varnished surfaces of either metal or wood which require rubbing with pumice, abrasive paper or cloth, or some similar material as a step in the finishing operation; I

One object of this invention is to prov de a small, light,-compact, high-speed machine whichv will have the functions above mentioned and which will provide a more ellicient meansof accomplishing the desired results than anything now in use.

Another object of the invention is to provide a machine which will bepractically impervious'to the dust and grit incident to the operation of a device of this kind.

It is not desired to limit the invention to the above usage, as it is apparent that it can be used fora-variety of brushing, burnishing, butting, polishing or sanding operations.

lVit-h these and incidental objects in view, the invention consists of certain novel features of construction and combinations of parts, the essential elements of which are set forth in appended claims and a preferred form or embodiment of which is hereinafter described with reference to the drawings which accompany and form part of this specification.

Of said figures:

Fig. 1 is a perspective View of the complete machine.

F'g. 2 is a detail isometric view of members which connect the pistons with the rubhing pads, one of said members being shown in section.

Fig. 3 is a detail isometric view of one of the pistons. I

Fig. 4 is a view inside elevation of the device with the top plate and the side plate removed.

Fig. 5 is a detail plan View of the bearing plate which is adapted to prevent any binding of the piston in the cylinder by reason of downward pressure exerted by the operator.

Fig. 6 is a sectional View showing the main inlet valve, and is taken on the line 66 of Fig. 4, looking in the direction of the arrows.

Fig. 7 is a view in end elevation with the end plate removed and some of the parts broken away for the sake of clearness.

Fig. 8 is a sectional view taken through the machine on the line 8-8 of Fig. 10.

Fig. 9 is a top plan View of the machine with the cover plate removed. 4

Fig. 10 is a vertical sectional View taken on the line 10-10 of Fig. 9, looking in the direction of the arrows.

Fig. 11 is a horizontal sectional View taken on the line 1111 of Fig. 8, looking in the direction of the arrows.

In general, the form selected to illustrate one embodiment of the invention, includes a body portion having parallelcylindrical holes bored thercthrough from end to end, the larger bore constituting a motor cylinder, and the small bore a valve chamber therefor.

Two double-headed pistons are arranged to traverse the cylinder, the pistons reciprocating simultaneously towards and from each other.

To accomplish this, valve mechanism in the smaller bore is controlled by one of the pistons to admit air pressure or other motive fluid alternately between the pistons to force the pistons apart. and. then to the ends of the cylinder to drive the pistons towards each other.

Provision is, of course, made to exhaust the spent fluid from in front of the pistons.

Fastened to each piston is a member which carries a rubbing pad of felt or any other suitable material which will be rapidly reciprocated by the action of the pistons to perform the rubbing operation. The members carrying the rubbing pads are connected to each other in such a manner as to sychronize their movement.

And in order to prevent as far as possible also expels that which may have worked its way into the casing.

Fast to each end of the body portion A (Fig. 11) of the device are two plates and 46, (Fig. 1) which are held in position by means of screws 47 and which closethe ends of the longitudinally extending operating cylinder 74, and valve chamber 71, respectively. A top plate 48 is fastened to the body portion A by long screws 49 (Fig.

7), the contour of said plate being formed to fit the palm of the hand of the operator. The plate is also provided with an upwardly extending thumb hold 40.

The upper edges of the end plates 45 and 46 extend above the top plane of the body portion A, and the top plate 48 fits closely between the end plates to exclude dirt and similar material.

The side edges of the end plates 45 and 46, as well as the side edges of the top plate 48, extend beyond the sides of the body portion A, the under face of such projecting edges of the top plate being grooved, as are also the projecting side edges of the end plates 45 and 46, to accommodate the top and end edges of two casing plates 50 extending along and covering the sides of the body portion A, and spaced apart therefrom. Fillet bars 51 (Figs. 4, 7, 8 and 11),

one on each side, are fastened to the main body portion A, near the lower edges of the casing plate 50, and are cut away at 52 (Fig. 11) to permit the connections between the pistons and the rubbing pads to be reciprocated, as will be hereinafter described. The casing plates 50 are held in place in tl1e)ir'grooves by screws 53 (Figs. 1, 4, and 11" Uomirol valve.

The air or other motive power, under pressure, is brought to the device through any suitable flexible tubing which is connected to an upwardly extending nipple 54, formed integral with the end plate 45. The nipple 54 contains an inlet passage 55, (Fig. 6) which conducts the pressure to the main control valve mechanism. This control valve mechanism includes a plunger 56 (Fig. 6)

slidably mounted in a cylindrical chamber 57 open at both ends and extending across the end plate 45. This plunger 56 is provided with two heads 58 and 59 spaced apart and normally located on opposite sides of the juncture of the passage 55 with the chamber 57, to prevent the escape of pressure when.

.valve chamber 71.

force the plunger 56 toward the left (Fig.

6) in order to keep the valve closed.

When it is desired to open the valve, the plunger 56 is moved toward the right (Fig. 6) by means of a lever 62 pivoted at 63 (Fig. 9) in a guide slot in the top plate 48. This lever is provided with a finger-hold 41 which, together with the thumb-hold 40 previously described, constitutes means by which the operator automatically applies pressure to open the valve as he grips the machine to place it on the article to be treated. Slots are cut in the walls of the valve chamber 57 (F ig. 1) at one end, to permit the lever 62 to completely open the valve. The opposite end of the lever 62 is provided with a cam portion 64, which, when the valve is closed, abuts against the wall of the guide slot formed in said top plate, (Fig. 9) and thereby limits the spring-actuated movement of plunger 56 toward the left (Fig. 6). The lever 62 carries a cap screw 65 which limits the movement of the lever toward the right. This screw can be adjusted to vary the amount of pressure admitted to the machine, which will, of course, control thespeed at which'it operates.

When the control valve is closed and the plunger 56 is returned to its left hand position, as shown in Fig. 6, the head 59 uncovers the end of a passage 66 communicating with the chamber 57, to permit the exhausted pressure in themachine to esca e quickly through the right hand end of the chamber 57 into the atmosphere. This rapid reduction of pressure is necessary to prevent an equalization of pressure on both sides of the operating pistons, hereinafter described, which would cause them to stop in the middle of their stroke. From this position they must be started manually.

Air intake.

When the control valve plunger 56 is moved toward the right (Fig. 6) by the lever 62, as above described, the head 59 will-uncover the end of the passage 66 to permit the motive fluid from the inlet 55 to enter passage 66, which leads downward and joins a horizontal passage 67 (Figs.'6 and 11) extending longitudinally of the body portion of the machine alongside the A valve bushing 70 (Fig. 10) 1s fixedly located in the valve chamber 71, intermediate its ends, the bushing, preferably having three peripherall extending grooves 69, 73 and 82 formedexteriorly thereof, and separate from each other. These grooves separated from each other by the intervening unreduced portions of the valve bushing, form outer pressure and exhaust chambers, annular in shape, each of which is connected by an annular row of ports with the hollow interior of the valve bushing. Thus annular series of ports 108 and 83 connect the annular chambers 73 and 82, respectively, with the interior chamber ofthe valve bushing.

The intermediate annular pressure chamber 69 is preferably Wider than the remaining annular chambers, and is provided with two annular rows of ports 72 and 105, respectively, located near the opposite ends ot'the chamber 69, and communicating with the hollow interior of the valve bushing 70.

A valve having three heads 88, 89 and 90 alined upon a single valve stem 87, is slidably mounted within the valve bushing, the intermediate head 88 being longer than the two remaining heads 89 and 90, to cover one or the other annular series of ports 72 or 105 leading from the outer annular pressure chamber 69 to the inner chambers 84 and 711 into which the hollow interior of the valve bushing is divided by the intermediate valve head 88. A large port 68 admits pressure from the passage 67 to the intermediate annular outer pressure chamber 69.

A combined inlet and exhaust'port 75 passing through the wall of the body portion between the valve chamber 71 and the piston cylinder 74 at a point substantially midway between the ends of the cylinder 71, affords direct communication between the outer annular chamber 73 and the piston cylinder.

Combined inlet and exhaust ports 79 formed in the ends of the body portion A (Figs. 7 and 10) lead from the opposite ends of the piston cylinder 74 to the opposite end of the combined inlet and exhaust passage 80 extending longitudinally through the body portion A from end to end thereof (Fig. 11), the ends of the passage 80 being closed by the end walls and 46.

The passage lies in substantially the same horizontal plane with the inlet passage 67, but along the opposite side of the body portion A, and is equipped with a port 81 (Fig. 11) communicating with the annular outer chamber 82.

The intermediate valve head 88 controls the two series of ports 72 and 105 between the intermediate annular pressure chamber 69 and the chambers 711 and 84 within the 'valve bushing, and the heads 89 and 90 control communication between the chambers 711 and 84 and the opposite ends of the valve chamber 71, by covering or uncovering the castellated openings 85 and 107 formed in the opposite ends of the valve bushing, respectively.

A plurality of exhaust tports 86 and 109 lead from opposite ends 0 the valve chamber 71, the large number of small ports shown being for the purpose of mufliing the noise of the exhaust.

Cylinder and pistons. As stated in the general description, the

machine has a single cylinder 74 in which operate two driving pistons 7 6 (Fig. 10) arranged in tandem in the cylinder. These pistons are of the double head variety and each head is grooved to accommodate a ring 77 of conventional design held against peripheral rotation by a pin 7 8 which projects into a slot in the ring. The pistons are adapted to reciprocate in opposite directions towards and from each other in the cylinder due to alternating periods of pressure and exhaustion between them and at their outer ends.

As shown in Fig. 10, the pistons are in their inner positions, and the slide valve is positioned to admit the pressure between the pistons 76 in order to force them to their outer positions at the ends of the cylinder 74.

Valve operating mechanism.

The valve heads 88, 89 and control the opening and closing of the intake and exhaust ports. The central head 88 of the three controls the intake of air, the right hand head 89 controls the exhaustion of air from the ends of the cylinder 74, and the left hand head 90 controls the exhaustion of air from between the pistons 76. The stem 87 of the valve has an extension 91 apertured to surround a ball 92 formed at a point about midway of the length of a lever 93. At its lower end this lever passes through an openingin the wall of the chamber 71, and carries a ball 94 which rests in a seat formed in a cap 95 screwed to the bottom of the main body portion A. The cap 95 acts as a fulcrum for the lever 93. At its upper end, the lever 93 passes through an elongated opening in the wall between the valve chamber 71 and the piston cylinder 74, and carries a head 101 cupped to surround a ball 102 formed on the lower end of a screw 103 which extends through the center of one ofand closing the valves at the correct time.

The following description of the operation assumes that at the time when the power was previously shut off by the manuallycontrolled valve 56, 58, 59, (Fig. 6) the parts came to rest in the positionsshown in Figs. 10 and 11.

When the operator is ready to use the machine, he places his hand on the formed top plate, his fingers falling naturally into the proper positions with the horn 40 in the space between the thumb and forefinger, the forefinger, lying in the curved finger piece 41 on the control lever 62.

Then by simply gripping the machine in the ordinary manner to lift it onto the work, the tension thus exerted rocks the control lever 62, the free end of which presses against the projecting end of the plunger 56 to slide the control valve to the .right (Fig. 6) against the tension of the restoring spring 60, until the head 59 uncovers the adjacent end of the passage 66, thereby permitting the pressure from the inlet to enter the passage 66.

The passage 66 conducts the pressure to passage 67 whence it is led through port 68 (Fig. 11) to the intermediate annular pressure chamber 69.

The intermediate valve head 88 blocks the annular series of ports 105 leaving the annular series of ports 72 uncovered. Hence the pressure passes through the ports 7 2 in- .to the interior chamber 711 formed in the valve bushing between the intermediate head 88 andthe end head 90. The head 90 covers the castellations 107 in the lefthand end (Fig. 11) of the valve bushing 70, so that the pressure can only escape from the internal chamber 711 through the annular row of ports 108 into the annular chamber 73(Figs. 11 and. 10) and thence, through the large port 75 to the space between the independent pistons 76, in the cylinder 74, here it operates to drive the pistons in opposite directions towards the opposite ends of the cylinder 74.

The fluid from the exhaust ends of the pistons 76, escapes through the exhaust ports 79 (Figs. 10- and 7) at the opposite ends of the cylinder, to the longitudinal passage 80 (Fig. 11) and thence, through the large I port 81 into the annular chamber 82 of the valve bushing, and through the annular row of ports 83 to the internal chamber 84 formed between the heads 88 and 89 of the slide valve.

The head 89 has uncovered the castellated ports 85 in the right-hand end (Fig. 11) of the valve bushing, so that the exhaust escapes from the internal chamber 84 through the ports 85 into the right-hand end (Fig. 11) of the valve chamber 71 and thence, through the muflling ports 86. As these mufliing ports 86; aswell as mufiiing ports 109 hereinafter referred to, are formed on both sides of the valve chamber 71, the exhaust passes therethrough into the space beoperation of the machine is prevented, in

great measure, from entering the machine and clogging or injuring the parts.

Particularly is this desirable when Working with pumice or other fine abradant material, which is dispersed by the operation of the machine on the work and if allowed to valve cause great enter the machine, and especially the and piston chambers, would quickly undesirable wear of the parts and damage to the machine.

Reverse cycle of operation.

The description of the operation thus far has included only the movement of the pistons 76 from their positions, as shown in F i 10, to their outer positions. Shortly be ore they reach these outer positions, the slide valve, which moves toward the left, due to its connection 93 with one of the pistons, slides the intermediate head '88 over the inlet ports 72, and thereby cuts off the supply of pressure from the annular pressure chamber 69 through ports 72, internal chamber 711, ports 108, annular chamber 73 to the port 75, between the pistons and also shifts the right-hand head 89 to cover the castellated exhaust ports 85 in the valve bushing 70, leading from the internal chamber 84 to the adjacent end of the valve chamber 71; and simultaneously shifts the opposite head 90 to uncover the castellated exhaust ports 107 leading from the internal chamber 711 to the valve chamber, thereby preventing the exhaust through castellated ports 85, and permitting exhaust through ports 107. A1-

,most at the same time the intermediate head 88 uncovers the annular row of ports leading from the annular pressure chamber 69 to the internal chamber 84 and the pressure is thereby permitted to pass from this chamber, through the ports 83 into the annular chamber 82, then through port 81, (Fig. 11) air passages 80 and ports 79 to both ends of the piston cylinder 74 to drive the pistons 76 toward the center.

This permits the exhaust pressure which is between the pistons 76 to be expelled through the control port 75, annular chamber 73, ports 108, internal chamber 711 and the openingsl07 in the castellated end of member 70, to the valve chamber 71 whence it exhausts through the middle exhaust openings 109 in the body portion A of the machine. Thus the cycle of operation of the pistons 76 is completed and they are returned to the positions in which they are shown in- The pistons 76 as they move towards and from each other, operate to rapidly reciprocate rubbing members or shoes over the material under treatment.

There are two rubbing pads or shoes 110 which are made of felt or any suitable ma-' terial. They are conveniently attached to the flat soles of metal shoes 111 by sharply pointed lugs 112 (Fig. 4) which project from said shoes. This method of mounting the pads greatly facilitates their engagement with the shoes 111.

These pads and shoes are reciprocated by the pistons 76 and are directly connected thereto by means of inverted U-shaped members 114, (Figs. 2, 4, 7, 8, 9, 10 and 11) ea h comprising a pair of legs connected at their upper ends by a flat web. At their lower ends these legs embrace the side edges of and are screwed to the pad-carrying shoes 111. Extending downwardly from the connecting webs of each of the U-shaped members are two spaced lugs 115 and 116 (Figs. 2, 8 and 10) which are adapted to fit into vertical channels 117 formed on each side of the center of the pistons 76, between the heads thereof (Fig. 3). The screw 103 and a similar screw 118 (Fig. 10) pass through countersunk holes 119 in the connecting webs to secure the members 114 rigidly with the pistons. To permit connection of the spaced lugs 115, 116 with their respective pistons 76, the lugs depend through elongated openings 741 (Figs. 8 and 10) extending longitudinally through the upper wall of the body portion A into the upper side of the piston cylinder, such.'openings lying between the heads of each piston and being of less length than the travel of the pistons so as to remain covered thereby at all times.

The lug and channel connection between the connecting webs 114 and pistons 76 permits the connections 114 to have vertical movement relatively to the pistons, so as to relieve the pistons of the thrust caused by the weight of the machine and such pressure as may be applied by the operator in using the machine, which thrust is transmitted through the shoes to the connecting members.

The under faces of the flat connecting webs between the legs supporting the shoes 111, extend over the fiat upper face 120 of the body portion A, and slide horizontally between the top surface 120 of-the main body portion and a replaceable bearing plate 121 (Figs. 4 and 5) which is supported on four small spacing blocks 122, one at each corner of the top face 120 of the main body portion. This bearing plate 121 is held in place by four screws 49 which extend through the spacing blocks 122 into the body portion, as shown in Fig. 7, and also serve to secure the top plate 48 in place. The bearing plate when worn, may be replaced by a new plate without necessitating replacement of the body portion A, or the top 7 plate 48. I

The function of the bearing plate 121 is to form a thrust surface with which the u per faces of the horizontal web portions 0 the U-shaped members 114 contacts to thereby lessen the wear on theupper half of the piston cylinder 74 which would otherwise occur if the pistons 76 had to take the upward pressure created when the operator presses down on the device.

By mounting the rubbing pads or feet 111 in such relation to the pistons 76 to which they are respectively connected that the centre of the foot lies in the same perpendicular line with a point midway between the ends of its piston, vibration of the parts is reduced as well as the tendency otherwise present, to cock or tilt the piston.

Syn chrom'ez'ng mechanism.

It is essential to the smooth operation of the device that the pistons be connected-for synchronous operation. This is accomplished by the following means. The adjacent edges of the horizontal webs of each of the U-shaped members 114 is complemcntarily stepped (Fig. 2) and has rigidly fastened to its farthest advanced step, a guide lug 124 from which projects a stud 125 (Figs. 2 and 4). These studs pass through guide slots 126 in the bearing plate 121, which slots embrace the guide lugs 124 to hold the connecting members 114 to a rectilinear movement. The upper ends of the studs 125 have loosely mounted thereon filler blocks 127 (Fig.9) which overlie and rest on the bearing plate 121. These filler blocks 127 are embraced by slots 128 out in the opposite ends of a rocker 129 which has a centrally located hub 130 (Fig. 10) projecting downwardly through a hole 131 in the stationary bearing plate 121, the lower end of the hub 130 passing between the stepped edges of the connecting members 114 and resting on the top face 120 of the main body portion of the machine. Projecting downwardly inside of the hub 130 is a pivot pin 132, the upper end of which has a circular cap flange 133 integral therewith and fastened to the under recessed face of the top plate 53 by screws 134.

It is apparent from the above that when the pistons are reciprocated as above described, the studs 125 carried by the U- shaped connecting members 114 will cause the filler blocks 127 to rotate the rocker 129 counter-clockwise when the pistons 76 move I dent that one of the pistons 76 cannot move without (the? other moving to exactly the sameextentdu' to the rocker connecting rocated U-shaped connecting members 114 are lubricated by means of oil dropping through two oil holes 135 (Figs. 5 and 10) in the bearing plate 121. The oil is distributed by oil grooves 136 in the under face of the bearing plate, leading from the oil holes 135. The oil can be su plied to the oil holes 135 from reservoirs f drmed in the under face of the top plate 48 to which access may be had through apertures closed by screw plugs 137 in the top plate 48.

The synchronizing rocker 129 is lubricated by an oil cup 138 (Fig. 10) cut in the pivot pin 132, from which a channel 139 leads to the bearing surface.

While the form of mechanism herein shown and described is admirably adapted to fulfill the objects primarily stated, it is to be understood that it is not intended to confine the invention to the one form or embodiment herein disclosed, for it is susceptible of embodiment in various forms all coming within the scope of the claims which follow.

What is claimed is:

1. In a machine of the class described, the combination of a cylinder, a piston operating therein, a pad-supporting member located below said cylinder, and a connection extending between the piston and' the pad-supporting member.

2. In a machine of the class described, the combination of a cylinder, a piston operating therein, a pad-supporting member located below said cylinder, a connection extending between the piston and the pad-support ing member, and a casing substantially enclosing said connection.

3. Ina machine of the class described, the combination of a cylinder provided with an opening through 1ts upper wall, a piston operating in said cylinder, a pad-supporting member located below said cylinder, and a connecting member between said piston and the pad-supporting member, including a portion secured to said piston and operating in said opening and another portion constituting a connection between said first-named portion and said pad-supporting member.

4. In a machine of the class described. the

' combination of a cylinder provided with an opening through 1ts up er wall, a piston er, a pad-supportoperating in said cylin ing member located below said cylinder, and v a connecting member between said piston and the pad-supporting member, including a portion secured to said piston and operating in said opening, a web portion extending laterally from said first-mentioned portion, and leg portions. extending downwardly from said web portion and connected at their lower ends to said pad-supporting member. 1

5. In a machine of the class described, the combination of a body portion having a cylinder provided with an opening through its upper wall, a piston operating in said cylinder, a pad-supporting member located below said cylinder, and a connecting member between said piston and the pad-supporting member, including a portion secured to said piston and operating in said opening, a web portion extending laterally from said first-mentioned portion, other leg portions extending downwardly from said web portion and connected at their lower ends to said pad-supporting member, a bearing plate overlying said web portion, and an enclosing casing for said cylinder and-plate, including filler members bearing against the lower edges of the sides of said body portion and provided with openings in which the leg portions of the connecting members freely operate.

6. In a machine of the class described, the combination'of a body portion having a cylinder provided with an opening through its upper wall, a piston operating in said cylinder, a pad-supporting member located below said cylinder, and a connecting member between said piston and the pad-supporting member, including a portion secured to said piston and operating in said opening, a web portion extending laterally from said first- Inentioned portion, and leg portions extending downwardly from said web portion, and connected at their lower ends to said padsupporting member, a bearing plate overlying said web portion, and an enclosing casing including side plates, and filler bars interposed between the side plates and the sides of said body portion, and provided with openings in which said leg portions of the connecting member freely operate, the body portion having exhaust ports located to cause the exhaust to travel out through said last-named openings.

7. Ina machine of the class described, the combination of a body portion having a cylinder formed therein, a piston operating in the cylinder, a casing spaced from said cylinder to form chambers about said cylinder, said casing being provided with openings into the chambers, a rubbing pad support,

combination of a body portion having a cylinder formed therein, a piston operating in the cylinder, a casing spaced from said body portion to enclose the latter, said casing being provided with openings, a rubbing pad support, and connections between said piston and said support the connections passing through and operating in said openings, the body portion having exhaust ports so located as to discharge the exhaust into the enclosing casing whence it escapes through said openings. I

9. In a machine of the class described, the combination of a body portion having a cylinder formed therein, a piston operating in the cylinder, a rubbing pad support, a con nection' between said piston and support including a horizontally-disposed web arranged so that a line at right angles through its center coincides substantially with a line at right angles through the middle ofthe axis of the piston.

10; In a machine of the class described, the combination of a hand grip horizontally disposed across the top thereof, a hearing plate located on the under side of said hand grip, reciprocating members each comprising a horizontal portion and downwardly extending portions, said horizontal portions contacting on their upper horizontal surfaces with said bearing plate, a cylinder located beneath said horizontal portion and between the downwardly extending portions of said reciprocating members, pistons operating in said cylinder and operatively connected vertically with the horizontal portion of the pistons; a rubbing foot for each piston, each rubbing foot so arranged that its side edges are spaced substantially equidistantly from a vertical plane extending along the longitudinal axis of the piston, and its end edges are spaced substantially equidistantly from a vertical plane extending through the transverse axis of the piston at right angles to the first-named vertical plane, the central point of the foot lying substantially in line with a point in the longitudinal axis of its piston equidistant from the ends of the piston.

12. In a machine of the class described, the combination with a body portion having a cylinder formed therein; of pistons operating in the cylinder; means to synchronize the operation of the-pistons; a rubbing foot operatively connected to each piston, the relation of each of the rubbing feet to its respective piston being such that the center of each foot will lie in substantially the same vertical plane with a point midway between the ends of the piston to which it is connected.

In testimony whereof I aflix my signature.

HOWARD B. sooTT. 

